// Copyright (C) 1998-2001 by Jason Hunter <jhunter_AT_acm_DOT_org>.
// All rights reserved.  Use of this class is limited.
// Please see the LICENSE for more information.

package com.oreilly.servlet;

import java.io.UnsupportedEncodingException;
import java.util.Vector;

import javax.servlet.ServletRequest;

/**
 * A class to simplify parameter handling. It can return parameters of any
 * primitive type (no casting or parsing required), can throw an exception when
 * a parameter is not found (simplifying error handling), and can accept default
 * values (eliminating error handling).
 * <p>
 * It is used like this: <blockquote>
 * 
 * <pre>
 * ParameterParser parser = new ParameterParser(req);
 * 
 * float ratio = parser.getFloatParameter("ratio", 1.0);
 * 
 * int count = 0;
 * try {
 *     count = parser.getIntParameter("count");
 * } catch (NumberFormatException e) {
 *     handleMalformedCount();
 * } catch (ParameterNotFoundException e) {
 *     handleNoCount();
 * }
 * </pre>
 * 
 * </blockquote>
 *
 * There's also a capability to find out if any required parameters are missing
 * from a request: <blockquote>
 * 
 * <pre>
 * ParameterParser parser = new ParameterParser(req);
 * String[] required = { "fname", "lname", "account" };
 * String[] missing = parser.getMissingParameters(required);
 * </pre>
 * 
 * </blockquote>
 *
 * The default charset for input parameters is ISO-8859-1 (Latin-1). If the
 * parameter values are encoded in another format, specify that using
 * setCharacterEncoding() before parsing. The parameter names currently have to
 * be in the Latin-1 character set: <blockquote>
 * 
 * <pre>
 * ParameterParser parser = new ParameterParser(req);
 * parser.setCharacterEncoding("Shift_JIS");
 * String japaneseValue = parser.getStringParameter("latinName");
 * </pre>
 * 
 * </blockquote>
 *
 * @see com.oreilly.servlet.ParameterNotFoundException
 *
 * @author <b>Jason Hunter</b>, Copyright &#169; 1998, 1999
 * @version 1.4, 2000/12/14, better checking the selected encoding is valid in
 *          setCharacterEncoding() thanks to Dewayne McNair
 * @version 1.3, 2000/05/17, added setCharacterEncoding()
 * @version 1.2, 2000/05/17, getBooleanParameter() now recognizes "on" and "yes"
 * @version 1.1, 1999/12/20, added getMissingParameters() method
 * @version 1.0, 1998/09/18
 */
public class ParameterParser {

    private ServletRequest req;
    private String encoding;

    /**
     * Constructs a new ParameterParser to handle the parameters of the given
     * request.
     *
     * @param req
     *            the servlet request
     */
    public ParameterParser(ServletRequest req) {
        this.req = req;
    }

    /**
     * Gets the named parameter value as a boolean, with true indicated by
     * "true", "on", or "yes" in any letter case, false indicated by "false",
     * "off", or "no" in any letter case.
     *
     * @param name
     *            the parameter name
     * @return the parameter value as a boolean
     * @exception ParameterNotFoundException
     *                if the parameter was not found
     * @exception NumberFormatException
     *                if the parameter could not be converted to a boolean
     */
    public boolean getBooleanParameter(String name) throws ParameterNotFoundException, NumberFormatException {
        String value = getStringParameter(name).toLowerCase();
        if ((value.equalsIgnoreCase("true")) || (value.equalsIgnoreCase("on")) || (value.equalsIgnoreCase("yes"))) {
            return true;
        } else if ((value.equalsIgnoreCase("false")) || (value.equalsIgnoreCase("off"))
                || (value.equalsIgnoreCase("no"))) {
            return false;
        } else {
            throw new NumberFormatException("Parameter " + name + " value " + value + " is not a boolean");
        }
    }

    /**
     * Gets the named parameter value as a boolean, with a default. Returns the
     * default value if the parameter is not found.
     * 
     * @param name
     *            the parameter name
     * @param def
     *            the default parameter value
     * @return the parameter value as a boolean, or the default
     */
    public boolean getBooleanParameter(String name, boolean def) {
        try {
            return getBooleanParameter(name);
        } catch (Exception e) {
            return def;
        }
    }

    /**
     * Gets the named parameter value as a byte
     *
     * @param name
     *            the parameter name
     * @return the parameter value as a byte
     * @exception ParameterNotFoundException
     *                if the parameter was not found
     * @exception NumberFormatException
     *                if the parameter value could not be converted to a byte
     */
    public byte getByteParameter(String name) throws ParameterNotFoundException, NumberFormatException {
        return Byte.parseByte(getStringParameter(name));
    }

    /**
     * Gets the named parameter value as a byte, with a default. Returns the
     * default value if the parameter is not found or cannot be converted to a
     * byte.
     * 
     * @param name
     *            the parameter name
     * @param def
     *            the default parameter value
     * @return the parameter value as a byte, or the default
     */
    public byte getByteParameter(String name, byte def) {
        try {
            return getByteParameter(name);
        } catch (Exception e) {
            return def;
        }
    }

    /**
     * Gets the named parameter value as a char
     *
     * @param name
     *            the parameter name
     * @return the parameter value as a char
     * @exception ParameterNotFoundException
     *                if the parameter was not found or was the empty string
     */
    public char getCharParameter(String name) throws ParameterNotFoundException {
        String param = getStringParameter(name);
        if (param.length() == 0)
            throw new ParameterNotFoundException(name + " is empty string");
        else
            return (param.charAt(0));
    }

    /**
     * Gets the named parameter value as a char, with a default. Returns the
     * default value if the parameter is not found.
     * 
     * @param name
     *            the parameter name
     * @param def
     *            the default parameter value
     * @return the parameter value as a char, or the default
     */
    public char getCharParameter(String name, char def) {
        try {
            return getCharParameter(name);
        } catch (Exception e) {
            return def;
        }
    }

    /**
     * Gets the named parameter value as a double
     *
     * @param name
     *            the parameter name
     * @return the parameter value as a double
     * @exception ParameterNotFoundException
     *                if the parameter was not found
     * @exception NumberFormatException
     *                if the parameter could not be converted to a double
     */
    public double getDoubleParameter(String name) throws ParameterNotFoundException, NumberFormatException {
        return new Double(getStringParameter(name)).doubleValue();
    }

    /**
     * Gets the named parameter value as a double, with a default. Returns the
     * default value if the parameter is not found.
     * 
     * @param name
     *            the parameter name
     * @param def
     *            the default parameter value
     * @return the parameter value as a double, or the default
     */
    public double getDoubleParameter(String name, double def) {
        try {
            return getDoubleParameter(name);
        } catch (Exception e) {
            return def;
        }
    }

    /**
     * Gets the named parameter value as a float
     *
     * @param name
     *            the parameter name
     * @return the parameter value as a float
     * @exception ParameterNotFoundException
     *                if the parameter was not found
     * @exception NumberFormatException
     *                if the parameter could not be converted to a float
     */
    public float getFloatParameter(String name) throws ParameterNotFoundException, NumberFormatException {
        return new Float(getStringParameter(name)).floatValue();
    }

    /**
     * Gets the named parameter value as a float, with a default. Returns the
     * default value if the parameter is not found.
     * 
     * @param name
     *            the parameter name
     * @param def
     *            the default parameter value
     * @return the parameter value as a float, or the default
     */
    public float getFloatParameter(String name, float def) {
        try {
            return getFloatParameter(name);
        } catch (Exception e) {
            return def;
        }
    }

    /**
     * Gets the named parameter value as a int
     *
     * @param name
     *            the parameter name
     * @return the parameter value as a int
     * @exception ParameterNotFoundException
     *                if the parameter was not found
     * @exception NumberFormatException
     *                if the parameter could not be converted to a int
     */
    public int getIntParameter(String name) throws ParameterNotFoundException, NumberFormatException {
        return Integer.parseInt(getStringParameter(name));
    }

    /**
     * Gets the named parameter value as a int, with a default. Returns the
     * default value if the parameter is not found.
     * 
     * @param name
     *            the parameter name
     * @param def
     *            the default parameter value
     * @return the parameter value as a int, or the default
     */
    public int getIntParameter(String name, int def) {
        try {
            return getIntParameter(name);
        } catch (Exception e) {
            return def;
        }
    }

    /**
     * Gets the named parameter value as a long
     *
     * @param name
     *            the parameter name
     * @return the parameter value as a long
     * @exception ParameterNotFoundException
     *                if the parameter was not found
     * @exception NumberFormatException
     *                if the parameter could not be converted to a long
     */
    public long getLongParameter(String name) throws ParameterNotFoundException, NumberFormatException {
        return Long.parseLong(getStringParameter(name));
    }

    /**
     * Gets the named parameter value as a long, with a default. Returns the
     * default value if the parameter is not found.
     * 
     * @param name
     *            the parameter name
     * @param def
     *            the default parameter value
     * @return the parameter value as a long, or the default
     */
    public long getLongParameter(String name, long def) {
        try {
            return getLongParameter(name);
        } catch (Exception e) {
            return def;
        }
    }

    /**
     * Determines which of the required parameters were missing from the
     * request. Returns null if all the parameters are present.
     * 
     * @param required
     *            array of required parameters
     * @return an array of missing parameters, or null if none are missing
     */
    public String[] getMissingParameters(String[] required) {
        Vector missing = new Vector();
        for (int i = 0; i < required.length; i++) {
            String val = getStringParameter(required[i], null);
            if (val == null) {
                missing.addElement(required[i]);
            }
        }
        if (missing.size() == 0) {
            return null;
        } else {
            String[] ret = new String[missing.size()];
            missing.copyInto(ret);
            return ret;
        }
    }

    /**
     * Gets the named parameter value as a short
     *
     * @param name
     *            the parameter name
     * @return the parameter value as a short
     * @exception ParameterNotFoundException
     *                if the parameter was not found
     * @exception NumberFormatException
     *                if the parameter could not be converted to a short
     */
    public short getShortParameter(String name) throws ParameterNotFoundException, NumberFormatException {
        return Short.parseShort(getStringParameter(name));
    }

    /**
     * Gets the named parameter value as a short, with a default. Returns the
     * default value if the parameter is not found.
     * 
     * @param name
     *            the parameter name
     * @param def
     *            the default parameter value
     * @return the parameter value as a short, or the default
     */
    public short getShortParameter(String name, short def) {
        try {
            return getShortParameter(name);
        } catch (Exception e) {
            return def;
        }
    }

    /**
     * Gets the named parameter value as a String
     *
     * @param name
     *            the parameter name
     * @return the parameter value as a String
     * @exception ParameterNotFoundException
     *                if the parameter was not found or was the empty string
     */
    public String getStringParameter(String name) throws ParameterNotFoundException {
        String[] values = req.getParameterValues(name);
        if (values == null) {
            throw new ParameterNotFoundException(name + " not found");
        } else if (values[0].length() == 0) {
            throw new ParameterNotFoundException(name + " was empty");
        } else {
            if (encoding == null) {
                return values[0];
            } else {
                try {
                    return new String(values[0].getBytes("8859_1"), encoding);
                } catch (UnsupportedEncodingException e) {
                    return values[0]; // should never happen
                }
            }
        }
    }

    /**
     * Gets the named parameter value as a String, with a default. Returns the
     * default value if the parameter is not found or is the empty string.
     * 
     * @param name
     *            the parameter name
     * @param def
     *            the default parameter value
     * @return the parameter value as a String, or the default
     */
    public String getStringParameter(String name, String def) {
        try {
            return getStringParameter(name);
        } catch (Exception e) {
            return def;
        }
    }

    /**
     * Sets the character encoding (charset) of the request to help the parser
     * properly decode parameter values. The default is to return undecoded
     * values, the same as would be returned by getParameter().
     *
     * @param encoding
     *            the charset of the request
     * @exception UnsupportedEncodingException
     *                if the charset is not supported on this sytem
     */
    public void setCharacterEncoding(String encoding) throws UnsupportedEncodingException {
        // Test the encoding is valid
        new String("".getBytes("8859_1"), encoding);
        // Getting here means we're valid, so set the encoding
        this.encoding = encoding;
    }
}
